but if I enter tom.tuningworks.ch, I doesn't work
---
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

Additionally, a 500 Internal Server Error error was encountered while trying to use an ErrorDocument to handle the request.
The subdomain function always links to the normal page, for instances if i deactivate the .httacess file, I normaly transfers tom.tuningworks.ch to
www.tuningworks.ch

The only thing i can think of is that your webserver is configured to allow only one redirect. we are using 2.

this would be mentioned in your error_log like the previous poster says. The logs are usualy located in a dir higher than your webroot and accessible by ftp, if not you can check your control panel if you have one.